Variable Clinical Classifications and Diagnostic Coding Systems of Colorectal Neuroendocrine Tumor

ABSTRACT

The incidence of colorectal carcinoid tumor is recently increasing as screening colonoscopy increased. Traditional carcinoid tumor had been known as low grade, malignant neuroendocrine cell orign tumor. In 2000, World Health Organization (WHO) suggested that carcinoid was called well-differentiated neuroendocrine tumor (NET). It recently updated in 2010 by WHO; according to the differentiation and malignant potential, NET classified with NET Grade 1, Grade 2, and neuroendocrine carcinoma. They suggested that NET had malignant potential in accordance with histopathologic characteristics. Therefore, WHO recommended the behavior code of NET as malignant. However, European Neuroendocrine Tumor Society (ENETS) proposed the behavior of NET to four grades based on the histopathologic features; benign, benign or low grade malignant, low grade malignant, and high grade malignant. Also, American Joint Committee on Cancer (AJCC) suggested that topography codes of NET were defined as malignant. Korean Standard Classification of Diseases (KCD) described the different codings of carcinoid (NET). The discrepancies of behavior code or coding system exist among WHO, ENETS, AJCC and KCD. Also, there were differences in the perception for topographic coding system between clinicians and pathologists. NETs of colorectum were reported with the variable clinical characteristics (especially, metastasis) and long term prognosis from many studies. Especially, risk of metastasis and long term prognosis of small sized NET (<1 cm) had some discrepancies and should be investigated prospectively. Therefore, the consensus about topographic codes of NET should be needed with multidisplinary approach among gastroenterologists, pathologists and surgeons.